Harris



Feb. 21, 1956 J. H. ENGEL 2,735,390 METHOD 0E PRODUCING DEEPDRAWN sHAPEs 1N SHEET METAL Filed July 28, 1952 2 Sheets-Sheet l iff/lll, 11

/N VEN Tof?. do HN H. ENGEL BY H/s ATTORNEYS.

i'ie ...ill/L44 o HH RR/s, Kn.c cH, Fos rsf? L HnRR/s Feb. 21, 1956 J. n. ENGEL 2,735,390

METHOD oF PRoDUcTNG DEEP-DRAWN sHAPEs 1N SHEET METAL Filed July 28, 1952 2 Sheets-Sheet 2 Fgfzz.

/NveA/Tol?. doH/v H. ENG/L BY H/S ATTORNEYS. 2l@ rek/s, K/EcH, Fos TER a: Heee/s of softer metals or other materials `ations such as hydro-pressing.

Another object of the invention is to provide a method NUSTHOD F PRODUCIN G DEEP-DRAWN SHAPES 1N SHEET NIETAL John H. Engel, Escondido, Calif. Application July 28, 1952, Serial No. 301,193 9 Claims. (Cl. 113-51) 'Ihis invention relates to metal forming or shaping by means of dies, and more particularly to apparatus and procedures for what is commonly known as deepdrawing.

Heretofore, in connection with the deep-drawing or stamping of metal sheets in the usual single step drawing operation, undue stretching and thinning or wrinkling of the metal, especially at sharp bends, have resulted and unsatisfactory products have as a consequence been turned out.

1t is an object of this invention to provide a method and apparatus for processing metal sheets, which are eventually to be shaped into deep drawn or crowned or cupped zones or with sharp bends, by first imparting to them a preliminary, moderate shaping by which portions of the metal sheet are so displaced that such preliminary displacement directly facilitates a subsequent shaping operation which normally would be quite severe if the usual drawing procedure were undertaken, but, in view of the preliminary shaping of the present improvement, merely constitutes another relatively mild shaping operation.

I have discovered a method for avoiding the abovedescribed diiculties, which method includes a preliminary partial stretching or shrinking, as the case may be, so that the metal sheet is preshaped to an intermediate stage, such preliminary shaping facilitating a subsequent or final shaping without undue stretching, or thinning, or buckling or wrinkling of the metal sheet at any place in any significant degree.

Another object of this invention is to simplify all deep-drawing procedures and kindred shaping procedures wherein the plural stage operations of this invention will yield improved shaped products.

Other objects of the invention are to make it possible to employ in any given connection smaller dies to obtain faster production, to reduce of elimination of damage to metal sheets undergoing drawing, to permit the use of cheap blanking dies, to reduce die shifting, to reduce shear-strain on equipment and procedures, to provide for wider use of the various metals, to permit the employment of metal sheets of thinner gages for yielding structures of less weight, to improve the structural condition of the product, to permit hot forming of some metals, and to permit the use for dies in some operfor deep-drawing and similar metal shaping whereby stretching, wrinkling, shrinking and the like may be uniformly controlled and in a predetermined manner, wrin- 'kling, stretching or shrinking being effected in predeter- `mined directions as best required to provide for the final shaping operation whether such nal operation be a stretching operation or effectively a shrinking operation.

It is a still further object of the invention to provide Vfor a preliminary wrinkling or waving of the metal sheet which is nally to be shaped into a given product,

material losses by reason United ,States4 PatcntO therefrom, these having such wrinkling or waving preferably being effected in general correspondence with the nature of the final shaping of the sheet, whether such shaping be by stretching or shrinking operations.

It is a still further object of the invention to employ a flexible, preferably non-stretchable, or only slightly stretchable, set, pattern material which has been shaped to conform exactly with the final product as by shaping to the final male or female die, such flexible, substantially non-stretchable pattern being then shaped into a desired wrinkle formation, as through the medium of any retaining'means such as modeling clay, fromwhich a pattern may be made for an intermediate or preforming die by means of which preforming die the sheets to be shaped will be given preforming treatment prior to final shaping in finish dies.

Other objects of the invention, and the various novel features thereof will become apparent to those skilled in the art upon reference to the following specification and the accompanying drawings wherein certain embodiments are illustrated.

' In the drawings, wherein the deep-drawing of a relatively simple shape is illustrated:

Fig. 1 represents a side elevation of a male finish die superimposed over a female finish die having the shape to be produced in the final product;

Fig. 2 illustrates diagrammatically the production of a flexible, relatively non-stretchable pattern from the male die member;

Fig. 3 indicates in vertical cross section a step of associating the pattern produced in Fig. 2 with retaining means such as modeling clay to be relied upon in a subsequent shaping operation;

Fig. 4 indicates in a vertical cross section the shaping by waving of the flexible, substantially non-stretchable pattern of Figs. 2 and 3 through the medium ofrelatively stiff modeling clay; t

Fig. 5 indicates diagrammatically how the curved strucvture 4of Figs. 2 and 3, which might be hemispherical, is

related to the waves of Fig. 4;

Fig. 6 is a fragmentary detail in plan showing a woven fabric imbedded in set latex material (or the like) of which the pattern is formed, a portion of the imbedding material being broken away to reveal the fabric;

Fig. 7 is a cross sectional detail taken on the line 7 7 of Fig. 6;

Fig. 8 is a sectional detail indicating'modified means (small tacks) of effecting the configuration of the flexible non-stretchable pattern;

Fig. 9 is illustrative of both a male plaster mold and preforming die, made therefrom, superimposed over a corresponding female mold and preforming die made been produced from the shaped pattern of Fig. 4 or of Fig. 8;

Fig. 10 illustrates a method from the female die of a heavy rubber blanket and a at hammer blanket;

Fig. l1 indicates the Fig. 10;

Fig. l2`is a plan View of the preformed metal sheet of Fig. 11, and consequently is also a plan view of the female die with which it was formed and of the flexible pattern;

Fig. 13 illustrates a final preformed sheet of Fig. 12;

Fig. 14 is an inner face View of the finally shaped article indicated in Fig. 13;

Fig. 15 is a perspective view illustrating the drawing of of shaping a metal sheet Fig. 9 through the medium of disposed above the metal sheet superimposed above the rubber action of the flat hammer of shaping operation upon the sharp corners `Fig. 16 is a fragmentary sectional detail showing the use of a thin liner or stage die in a finish female die toprovide an intermediate curve at the sharp shoulder position of Fig. 15, an intermediate male die being employed; and

Fig. 17 is a sectional'detail indicating a finalV operation in producing a sharp shoulder with the two finish dies after the liner orstage die of Fig. 16 has been removed.

In practicing this invention, a finish Vmale die yand a finish female die 12, illustrated in Fig. l, twill yhave been manufactured to produce the required product. Eithe'r of the finish dies Ill and `12, but preferablythe male die '19 is used in the nature of a pattern to form thereon an 4accurate set, flexible, relatively Anon-stretchableipatte'rn 1S indicated in Fig. 2. 'This pattern 15, which @includes a 4large crowned or cupped zone, is made up of appropriate lfabric l16, such as cheeSecloth, andan appropriate setting rn'aterial 18 `which is flexible when set, such as latex or is made without cheesecloth, but with a heavier layer of `latex so as to minimize stretching. LIn building the pattern 15, latex gum or other appropriate -forrn of rubber in the non-set state is first applied `to the shaping ksurface of vthe male die. A sheet :of `cheeseclothis then 'applied to the unset latex and pressed -down into 'the same, or if necessary a number of pieces of cheesecloth are applied to the latex in various positions and Vin overlapping relationship, so that the shape ofthe 'formingmeinber of the die is attained by the applied cheesecloth. Preferably, additional latex Vis applied `over the .positionedcheesecloth :('an'd a second layer of cheesecloth is positioned) whereupon another layer of the latex material is applied. This `operation lis readily effected manually and the latex and cheesecloth llayers so worked that Vthe layers are thorough- 1y saturated with the latex and one uniform whole vis produced which exactly conforms to the shape of the forming portion of the die. This pattern member is then allowed to set on the die. When thoroughly-set, the pattern member 1S is readily stripped off from ythe die. The layers of 'cheesecloth used are adequate to render the pattern non-stretchable in any direction, although the latex land bedding material yrender the pattern Vflexible so that it may be shaped into a plurality of wrinklesas best indicated Iin Fig. 4.

For the purpose of simplicity, the forming member of the male die 10 is considered to be aLpor-tion of a sphere, the pattern 15 therefore being circular, as -is the preformed metal sheet of Fig. 12 and the lfinally shaped product of Fig. 14.

In order to produce a preforming die, such as seen in Fig. 10, from the cupped .pattern 15, the 'latter is placed upon an appropriate support (Figs` 3, 4 and 8), and the cup portion is then rather carefully worked vinto a series of'wrinkles or waves 22 as seen lin Fig. 4. ln the case of the partially spherical structure illustrated, -these wrinkles may desirably be in the form of circular concentric waves. lt is necessary of course that the position of these concentric waves be `maintained in order that plaster casts or the like may be made-from `whichto-pro duce the required preforming die or 'dies vsuch as 'illustrated in Fig. 9. In Figs. 3 and 4 the means employed for `retaining the shape of the waves 22 is inthe form lof modeling clay 24 or the like. This clay yis rather 'readily shapable by the fingers of the operator as the waves are being produced in the fabric body of the pattern 15. Having thus been shaped, the waves orV wrinkles readily maintain themselves in coniunction with the conforming shapes .in the modeling clay. lf essential, very small itacks'such as indicated at 2S may be Aplaced at the `bottoms of ithe waves and driven into the base 20 which maybe a -wood base. Commonly such tacks are not necessary. Another method for maintaining the wrinkles or waves 22 :in the pattern 15 is illustrated in Fig. 8 where flat headed tacks A26a-re employed to anchor the bottoms of the wrinkles. In practice the heads of these tacks will be .imb'ed'dedin the fabric-latex layer so as not to kinterfere appreciably with the subsequent forming of castings for Vthe preform- "pattern is then employed Ifor the casting ing dies. 'Of course, in more complex structures, the waves or wrinkles produced in the cupped pattern 15 will be quite variable and may be quite irregular according to the shape of the pattern and the final product to be obtained. If necessary to provide a marginal retainer to facilitate shaping, such as indicated at 28 in Fig. 4, such may be employed, although probably this will not be necessary.

By referenceto the `diagrammatic.indication of Fig. 5, wherein a segment is illustrated representing an elongation of about 20% of the arc, it will be seen that, when the cup portion of the :pattern 15 iis pressed down and the waves or wrinkles 22 lformed, theelongation is taken up by the resultant undulations. This i's true not only on the diameter indicated'in Fig. 5, but also on the circles indicated in Fig. 12.

Having shaped the cupped pattern 15 to provide appropriate waves or wrinkles 22 as seen in Fig. 4, this shaped lthereupon of a plaster 'o'r other appropriate l`I riold, from which thefnecessary prefo'rinin'g dies `are produced. Thus -a plaster -oast 30 representing a preforming female die may be formed, and a plaster cast 32 representing apreformi'ng Smale die may also be formed. lhese'o'asts 30 and 32 arethenfus'ed as molds to produce the-required preforniing dies. Both a male die and a `female die maybe used (of which also `Fig. 9 'may be considered representative), or, asi-indicated in Figs. 10 and 1l, a female die 35 may be employed :in

conjunction with =a typical rubber -blanket'or pad -36 and a fiat hammer 38 which may have-a pad-'retainingitlange 39 if necessary'or desirable. Bymeans of such-llat-hamner 38 and 4the rubber pad 36, which is formed from a tough, fairly hard rubber having a Shore fhardnessof 40 to v9() or harder .(and corresponding 'generallywithtruck tire tread stock), a lblow 'of -the flat hammer 38 causes 'the metal sheet 40, which has been Ainserted Vin the position shown -in Fig. '10, 'readily lto assume the -shape of `the female die by reason lof distortion of the rubber pad 40, as shown in Fig. l1. The preformed metal sheet 40 thus formed has waves or wrinkles 42 corresponding with the waves orwrinkles 22 of the pattern V15, as lillustrated in both Figs. 'lil and 12. This is substantially the same shape that would have been imparted by employing a .preforrning male die `in conjunction with a -preformn'g female die 3S.-

By employing the intermediate preforming procedure described, it iis possible to use softer `materials fo'r the preforming dies than for the finish ydies. It would Veven be possible to employ a preforming male die of ylead or of a plastic 'material in conjunction with a female die 35 which probably would preferably be producedrof a harder material.

Having Vpreformed the sheet 40 t`o such 'a shape as indicated at 42 vin Fig. J12, it `is ythen passed to vtliefinish dies of Fig. 1, as shown in Fig. 13 wherein the female nish die l12 yis employed with'theimale finish fde 10, the final-ly Vshaped metal Sart-icle 50 "produced from the "p'r'eformed sheet 42 'being shown Yin position lin ythe female die 12 and beingseparatel-y shown in face view-in Fig-.114. It '-is desirable in some instances to employ a rubber blanket S5 interposed between the lfinish dies 10 and -12 in producing the finished article k50 whereby best to .produce the final displacement.

Much more complicated shapes may, of fcourse, lbe produced than that above described. Representatives 'of `suchshape's is the shape `A60 seen in Fig. 15, whereindeep- `drawn 'cupped portions run off at 'various Sangles to one 'another and sharp shoulders areto be produced 4-at- 62, liangediportions 64 'bein-g vrequired lin the final shape. [n `producing this shape various 'wrinkles 'and-waves 'will lb'eforlmed in the flexible, relatively non-stretchable pa't- :tern which will have been'produced to conform with the unal shape required, su'h pattern 'having been frnae Ls yabove'descifibedlinconnection With'tlepa'ttern 15. Additionally, .in the :1li-fst prefolnfiing 'operation `sinall 'w'rin'lles nay have been produced in the flanged portions 64 such as indicated at 65, these being the result of an initial contrasting effect, such contraction to be completed in a final forming stage. In this case, it is desirable to form the sharp shoulders in two stages of the final shaping operation, following the preforming operation. For this purpose a liner diel 70 (Fig. 16) will be used in the finish die 75 so that when a cooperating die 76 is brought down, the shoulder 62 will be formed as a rounded shoulder rather than as a sharp shoulder. Thereafter, a cooperating finish die 78 will be used with the lower finish die 75 to complete a sharp shoulder in the product 60 as seen in 62a in Fig. 17.

From the foregoing description it will be apparent that I have provided a method and means for producing shapes, especially deep-drawn or cupped or crowned shapes, which avoid over-stretching and thinning out of sheet material from which the shapes are being formed, :such method including essentially a preforming operattion, by means of which intermediate shaping is produced :as by the formation of waves or wrinkes so as to displace starting material in a general plane or zone which is relatively fiat or shallow as compared with the final deep-drawn product, the metal of the sheet being displaced in such preforming operation in directions and in a manner dissimilar to those of the final shape, the final shape being thereafter produced in a separate operation by finish dies which may be of conventional type. As a consequence of such intermediate or preforming operation, dies of softer material may be used for the preforming step, complete accuracy of manufacture of such preforming dies being unnecessary in view of the fact that such preforming step is an intermediate operation. The usual, accurate finish dies which are employed in the final step have a considerably longer life than where complete shapes are formed in one operation. Also the savings resulting from the spoilage of much starting material, as has heretofore resulted, are of very great significance. In addition the amount of highly skilled labor normally required is by this method very materially reduced.

Not only may softer metals than usual be employed for the preforming dies than are required for finish dies, but, for some uses, hard plastics and the like may also be used. If two preforming dies are employed for a given operation, it is feasible to make the male die of a material such as lead for many uses.

Sheets which may be readily drawn to yield true, uniform, and accurate products, without spoilage, are represented by aluminum alloys, magnesium alloys, stainless steels, and the like. Where final products of distinctly irregular shape are to be drawn, such as illustrated in Fig. 15, it is apparent that in wrinkling or Waving, at least in portions thereof, the pattern 15 must be shaped with fine waves or wrinkles of varying sizes and extending in varying and irregular directions according to the final shape required. Such methods are readily learned by operators of ordinary skill or of even less skill than that frequently required in conventional deep-drawing operations.

This process permits the employment of lighter and thinner materials than it has heretofore been possible to use in contoured stampings and the like; also magnesium or titanium sheets may be readily used with necessary controlled heating, as by employing heated rubber pads in connection with the preforming operation. Thus, the natural characteristics of both the process and the magnesium sheet undergoing elongation with controlled heating, provide great possibilities in corresponding large complicated stampings, and in addition reinforcements and auxiliary or complicated assemblies are avoided. These advantages offer great aid to the manufacture of lighter and more efficient aircraft and the like.

1. A method for producing deep-drawn shapes in metal sheets, including: forming a flexible pattern. having a cupped portion of the final shape required; shaping said cupped portion of the flexible pattern into a series of waves disposed in a generally flatter zone than the final shape required while avoiding increase in the projected area of the pattern; producing a preforming die conforming with said shaped flattened cupped portion of said fiexible pattern; shaping a metal sheet from said preforming die, thereby partially stretching and shrinking and partially shaping said sheet; and thereafter subjecting such preformed sheet to the action of finish dies to yield the final shape required.

2. A method for producing shapes from metal sheets, including the steps of: forming a flexible, relatively nonstretchable pattern conforming with the final metal shape having a cupped portion desired; shaping said flexible pattern by fiattening said cupped portion to provide a series of wrinkles in a flatter region than the final shape while avoiding increase in the projected area of the pattern; positioning said shaped pattern for casting; producing a cast mold conforming with said flattened shaped pattern; producing a preforming die from said cast mold and conforming therewith; operating upon a metal sheet with said preforming die and thereby partially shaping said sheet; and thereafter subjecting such partially shaped sheet to the action of a finish die to complete the desired metal shape.

3. A method as in claim 2 including the step of employing a yielding putty-like material in shaping said fiexible pattern to retain the wrinkled condition produced therein.

4. A method for producing deep-drawn shapes in metal sheets, including: forming a now-expanding flexible pattern having a cupped portion of the final shape required; shaping by depressing the cupped portion of the flexible pattern toward a flat plane into a series of wrinkles without material increase in the projected area of the cupped portion of the pattern and of the final shape and in a relatively flat wrinkled zone compared with the final deepdrawn shape; producing a preforming die conforming with said flattened wrinkled pattern of such limited area; preshaping a sheet of metal with said preforming die to conform with such die and thereby partially shaping said sheet; and thereafter shaping the preformed sheet with a finish die to yield the finally required cupped shape.

5. A shaping method as in claim 4 wherein the flexible pattern of the final shape is dome-like and the wrinkles are annular.

6. A method as in claim 4 wherein said preshaping is effected by disposing said metal sheet between a tough rubber blanket and said preforming die, said blanket holding said sheet, and then imparting drop-hammer irnpact to said sheet through said blanket to accomplish said preshaping.

7. A method as in claim 4 wherein putty-like material is disposed in the wrinkles produced in depressing said cupped pattern to maintain uniform surfaces of said wrinkles and avoid collapse thereof.

8. A method as in claim 4 wherein a plaster cast is produced from said flattened wrinkled shape and said preforming die is produced from said plaster cast.

9. A method for producing deep-drawn shapes in metal sheets, including: forming a flexible pattern of a final shape desired having a cupped portion; shaping the cupped pattern portion by depressing the same toward a fiat plane while forming a plurality of wrinkles; producing a preforming die from and conforming with said wrinkled depressed pattern portion; producing a preformed metal sheet from such preforming die; placing such preformed metal sheet between male and female finish dies; disposing a heavy rubber blanket on such preformed sheet in position spanning the female die and in position retaining the preformed sheet; and shaping to yield the final deep-drawn shape required.

References Cite in the le "of this patent UNITED STATES PATENTS Lvingtone Y..- Feb. 1'4, 1905 .Hardie i Oct. 27, 1908 May Nov` 22, 1927 Kamarzin Jan. 15, 1929 Tarbox Jan. 3, 1933 Vehko v. f July 18, 1939 Becker Mar. l1, 1941 8 Dulmage f...- v Ian. 13, 1942 Lyon f Dec. 8, 12942 Waters Mr. 9, 19743 Berger June v5, 1945 Burger et al. Aug. 28, 1945 Champer Feb. 1.1, 1947 Johnson Mar. 22, 1949 Bentsen Jan. 24, 1950 lFOREIGN PATENTS yGreat Britain v1903 Great Britain June 1, 1922 

